As　one　of　the　three　key　components　of　photodynamic　therapy　(PDT),　photosensitizers　(PSs)　greatly　influence　the　photodynamic　efficiency　in　the　treatment　of　tumors.　Photosensitizers　with　tetrapyrrole　structure,　such　as　porphyrins,　chlorins　and　phthalocyanines,　have　been　extensively　investigated　for　PDT　and　some　of　them　have　already　received　clinical　approval.　However,　only　a　few　of　porphyrin-based　photosensitizers　are　available　for　clinical　applications,　and　PDT　has　not　received　wide　recognition　in　clinical　practice.　In　this　regard,　PSs　remain　a　limiting　factor.　Our　research　focuses　on　the　rational　design　of　new　PSs.　Photocyanine,　a　Zinc　(II)　phthalocyanine　(ZnPc)　type　photosensitizer　with　low　dark　toxicity　and　high　single　oxygen　quantum　yield,　is　one　of　the　promising　PSs　candidates　and　currently　being　tested　in　clinical　trials.　Here,　we　present　an　overview　on　the　development　of　Photocyanine,　including　its　design,　synthesis,　purification,　characterization　and　preclinical　studies,　wishing　to　contribute　to　the　research　of　more　promising　PSs.